1. Field of the Invention
The present invention relates to an endoscope in which a bending portion performs a bending motion in conjunction with an operation of tilting a bending lever.
2. Description of the Related Art
Conventionally, endoscopes have been widely used in medical and industrial fields. Some endoscopes are provided with an elongated and flexible insertion portion. In general, such flexible endoscopes are provided with a bending portion capable of freely performing a bending motion in a predetermined direction in accordance with a user's manual operation, on a distal end side of the insertion portion.
Among the endoscopes, especially in a small-diameter endoscope for which an amount of force for bending is small, and the bending portion of which bends with a small radius of curvature, such as a bronchial endoscope, each portion is generally configured so that a grasping portion provided on the operation portion is grasped by three fingers of a middle finger, a third finger and a little finger of a left hand, a bending lever is operated by a thumb, and various kinds of switches/buttons such as a suction button are operated by a forefinger. Further, in order to easily realize a similar operation not only by a left hand but also by a right hand on an endoscope of this kind, for example, Japanese Patent Application Laid-Open Publication No. H8-299255 discloses a technique in which the bending lever is extended backward from a side portion of the operation portion in an L shape, a finger hooking portion is disposed on a back side of the operation portion, and a suction button is disposed on a longitudinal-direction central axis of the operation portion, on a switch portion set on a front side of the operation portion.
By the way, as for the endoscope with a small diameter, such as a bronchial endoscope, it is also demanded to cause the bending portion to perform a bending motion not only in two directions, such as up and down directions, but also in any of directions including up, down, left and right directions. As a technique for realizing such a bending motion by an operation input to a single bending lever, for example, Japanese Patent Application Laid-Open Publication No. 2003-325437 discloses a bending apparatus provided with a wire pulling member having four arm portions to which proximal end portions of pulling wires (pulling members) corresponding to up, down, left and right bending directions are fixed, respectively, and an operation instruction lever (bending lever) for giving an instruction to cause a tilt direction of and an amount of tilt of the wire pulling member to change and cause a predetermined pulling wire, among the respective pulling wires, to move by a predetermined amount.